1. Field of the Invention
The present invention relates to a gas safety detector, and more particularly to a gas safety detector having a self-detection function.
2. Description of the Related Art
A conventional gas safety detector comprises a sensor mounted on the ceiling to detect existence of the gas. When the sensor detects that the gas concentration in a site, such as the house or the like, exceeds a predetermined limit, the gas safety detector emits an alarm signal by blinking, buzzing or the like so as to warn the user, thereby protecting the user's safety. However, the gas safety detector cannot be operated normally when the sensor is inoperative or worn out, thereby causing danger to the user.
A conventional gas safety detector having a self-detection function in accordance with the prior art shown in FIG. 4 comprises a base board 80, a step motor 81 mounted on a first side of the base board 80, a rotation member 82 rotatably mounted on the step motor 81, a drive rod 83 mounted on the rotation member 82 to rotate therewith, a gas device 84 mounted on a second side of the base board 80 and having an end provided with a retractable nozzle (not shown), a link 85 pivotally mounted on the base board 80 and having a first end rested on and driven by the drive rod 83 and a second end formed with a hook portion 850 hooked on the nozzle of the gas device 84, a substantially Z-shaped catch plate 87 having a first end secured on the base board 80 and a second end rested on a mediate portion of the link 85, and a sensor 86 mounted on the second side of the base board 80 and located adjacent to the nozzle of the gas device 84.
In operation, the rotation member 82 is rotated by the step motor 81 to rotate the drive rod 83 which presses and moves the first end of the link 85 to pivot the link 85 by a leverage action to drive the hook portion 850 of the second end of the link 85 to pull the nozzle of the gas device 84 outward, so that the gas contained in the gas device 84 is ejected outward. At this time, the link 85 is limited by the catch plate 87 to prevent deflection of the link 85 due to an excessive hit of the drive rod 83. In practice, when the sensor 86 is operated at the normal state, the sensor 86 can detect the escaped gas from the nozzle of the gas device 84 and emits a warning signal in an optical or audible manner. Alternatively, when the sensor 86 is not operated at the normal state, the sensor 86 cannot detect the escaped gas from the nozzle of the gas device 84 and emits a warning signal after the gas enters the sensor 86, so that the sensor 86 needs to be repaired or replaced for safety. After the gas is ejected outward from the gas device 84, the step motor 81 is operated reversely to return the drive rod 83 to the original position to release the link 85 which releases the hook portion 850, so that the retractable nozzle of the gas device 84 is returned to the original position to stop flow of the gas. In such a manner, the gas enters the sensor 86 to perform a self test so as to identify if the sensor 86 is operated at the normal state, so that the gas safety detector has a self-detection function to detect the working state of the sensor 86 so as to ensure the safety o f the gas safety detector when in use.
However, movement of the link 85 is limited by the catch plate 87, so that when the pressing force of the catch plate 87 is too large, operation of the link 85 is interrupted so that the link 85 cannot return to its original position easily, and when the pressing force of the catch plate 87 is too small, the link 85 is easily driven by the drive rod 83 to move upward to have an inclined angle, so that the catch plate 87 is jammed by the link 85. In addition, the step motor 81 is in line with the link 85, and the gas device 84 is perpendicular to the link 85, so that the conventional gas safety detector has a larger volume, thereby occupying a larger space. Further, the step motor 81 increases costs of the conventional gas safety detector. Further, when the step motor 81 stops operating due to a malfunction or electric shutoff, movement of the drive rod 83 is stopped, and the hook portion 850 of the link 85 still pulls the nozzle of the gas device 84 outward, so that the gas contained in the gas device 84 is ejected outward successively, thereby causing danger.